Acoustic wave device

Abstract

An acoustic wave device includes first and second acoustic wave resonator units. In a first IDT electrode of the first acoustic wave resonator unit, an intersecting width region includes a central region and first and second low acoustic velocity regions at outer side portions of the central region. The first and second high acoustic velocity regions include openings along an acoustic wave propagation direction. In the second acoustic wave resonator unit, a second IDT electrode includes a central region and first and second low acoustic velocity regions at outer side portions in an intersecting width direction of the central region. At an outer side portion of the first low acoustic velocity region, openings are at a third busbar. At an outer side portion of the second low acoustic velocity region, openings are not provided for a fourth busbar.

What is claimed is: 
     
         1 . An acoustic wave device comprising:
 first and second acoustic wave resonator units;   a piezoelectric substrate;   a first IDT electrode on the piezoelectric substrate and defining the first acoustic wave resonator unit;   a second IDT electrode on the piezoelectric substrate and defining the second acoustic wave resonator unit electrically connected to the first acoustic wave resonator unit; and   an inter-stage connection portion connecting the first acoustic wave resonator unit and the second acoustic wave resonator unit; wherein   the first IDT electrode includes:
 a first busbar; 
 a second busbar spaced apart from the first busbar; 
 a plurality of first electrode fingers extending toward the second busbar and including one ends connected to the first busbar; and 
 a plurality of second electrode fingers extending toward the first busbar and including one ends connected to the second busbar; 
   the second IDT electrode includes:
 a third busbar; 
 a fourth busbar spaced apart from the third busbar; 
 a plurality of third electrode fingers extending toward the fourth busbar and including one ends connected to the third busbar; and 
   a plurality of fourth electrode fingers extending toward the third busbar and including one ends connected to the fourth busbar;   in each of the first and the second IDT electrodes, a central region is provided in a central portion of a direction in which the first and the second electrode fingers or the third and the fourth electrode fingers extend;   first and second low acoustic velocity regions in which acoustic velocities are lower than those in the central region are provided at both outer side portions of the central region in the direction in which the first and the second electrode fingers or the third and the fourth electrode fingers extend;   first and second high acoustic velocity regions in which acoustic velocities are higher than those in the central region are provided at both outer side portions of the first and second low acoustic velocity regions in the direction in which the first and the second electrode fingers or the third and the fourth electrode fingers extend;   in the first and the second high acoustic velocity regions in the first IDT electrode, a plurality of openings are provided along an acoustic wave propagation direction in both of the first and the second busbars;   of the third and the fourth busbars in the second IDT electrode, in the first high acoustic velocity region of the third busbar, a plurality of openings are provided along the acoustic wave propagation direction; and   in the fourth busbar, openings are not provided in the second high acoustic velocity region.   
     
     
         2 . The acoustic wave device according to  claim 1 , wherein the first acoustic wave resonator unit and the second acoustic wave resonator unit are connected in series. 
     
     
         3 . The acoustic wave device according to  claim 1 , wherein the piezoelectric substrate includes a high acoustic velocity member and a piezoelectric film laminated on the high acoustic velocity member, and the high acoustic velocity member is made of a high acoustic velocity material in which an acoustic velocity of a propagating bulk wave is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric film. 
     
     
         4 . The acoustic wave device according to  claim 3 , wherein the high acoustic velocity member is a support substrate made of the high acoustic velocity material. 
     
     
         5 . The acoustic wave device according to  claim 3 , further comprising a low acoustic velocity film laminated between the high acoustic velocity member and the piezoelectric film and made of a low acoustic velocity material in which an acoustic velocity of a propagating bulk wave is lower than an acoustic velocity of a bulk wave propagating through the piezoelectric film. 
     
     
         6 . The acoustic wave device according to  claim 3 , further comprising a support substrate supporting the high acoustic velocity member. 
     
     
         7 . The acoustic wave device according to  claim 1 , further comprising at least one acoustic wave resonator unit such that the acoustic wave device includes a plurality of acoustic wave resonator units including the first and the second acoustic wave resonator units. 
     
     
         8 . The acoustic wave device according to  claim 1 , wherein the inter-stage connection portion defines and functions as the second busbar and the third busbar. 
     
     
         9 . The acoustic wave device according to  claim 1 , wherein the plurality of openings in the first and second busbars and the plurality of openings in the third busbar are at least partially surrounded by the respective first, second, or third busbar. 
     
     
         10 . The acoustic wave device according to  claim 9 , wherein at least one of the plurality of openings in the first and second busbars and the plurality of openings in the third busbar is entirely surrounded by the respective first, second, or third busbar. 
     
     
         11 . The acoustic wave device according to  claim 1 , wherein the plurality of openings in the first and second busbars and the plurality of openings in the third busbar are entirely surrounded by the respective first, second, or third busbar. 
     
     
         12 . The acoustic wave device according to  claim 1 , wherein the first busbar includes an inner busbar portion, an outer busbar portion, and a linking portion connecting the inner busbar portion and the outer busbar portion. 
     
     
         13 . The acoustic wave device according to  claim 1 , further comprising a common busbar including a portion of the first busbar and a portion of the second busbar. 
     
     
         14 . The acoustic wave device according to  claim 6 , wherein the support substrate includes a semiconductor or an insulator. 
     
     
         15 . The acoustic wave device according to  claim 14 , wherein the semiconductor includes silicon. 
     
     
         16 . The acoustic wave device according to  claim 14 , wherein the insulator includes Al 2 O 3 . 
     
     
         17 . The acoustic wave device according to  claim 3 , wherein the high acoustic velocity member includes at least one of aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, silicon, sapphire, lithium tantalate, lithium niobate, crystal, alumina, zirconia, cordierite, mullite, steatite, forsterite, magnesia, a diamond-like carbon (DLC) film, or diamond. 
     
     
         18 . The acoustic wave device according to  claim 5 , wherein the low acoustic velocity film includes at least one of silicon oxide, glass, silicon oxynitride, tantalum oxide, a compound obtained by adding fluorine, carbon, boron, hydrogen, or a silanol group to silicon oxide.